1. Technical Field of the Invention
The present invention relates to novel cosmetic compositions for topical application, for the photoprotection of the skin and/or the hair against ultraviolet radiation (such compositions hereinafter simply designated "sunscreen," "sunscreen/cosmetic" or "photoprotective/sunscreen" compositions), and to the use of same for the cosmetic applications indicated above.
This invention more especially relates to the aforesaid sunscreen/cosmetic compositions comprising, in a cosmetically acceptable vehicle, carrier or diluent, typically an oil-in-water emulsion, combinatory immixture of (i) at least two particular and unique sunscreen compounds, namely, on the one hand, 2,4,6-tris[p-((2'-ethylhexyl)oxycarbonyl)anilino]-1,3,5-triazine and, on the other, benzene-1,4-di(3-methylidene-10-camphorsulfonic)acid, and (ii), as photoprotective agents that function by physically blocking radiation (UV diffusers and/or reflectors), inorganic nanopigments based on metal oxides, in particular on titanium dioxide. This admixture imparts enhanced solar protection factors to the subject compositions via an unexpected synergistic effect.
2. Description of the Prior Art
It is well known to this art that light radiation of wavelengths of from 280 nm to 400 nm promotes tanning of the human epidermis, and that irradiation of wavelengths of from 280 to 320 nm, i.e., UV-B irradiation, causes erythema and burning of the skin which can impair the development of a natural tan; hence, such UV-B radiation must thus be screened from the skin.
It is also known to this art that UV-A radiation, of wavelengths from 320 to 400 nm, which tans the skin, also adversely affects it, in particular in the event of sensitive skin or a skin which is continually exposed to solar radiation.
UV-A rays cause, in particular, a loss in the elasticity of the skin and the appearance of wrinkles, promoting a premature aging thereof. Such irradiation promotes triggering of the erythematous reaction or enhances this reaction in certain individuals, and may even be the source of phototoxic or photoallergic reactions. Thus, it is desirable to also screen out UV-A radiation.
A wide variety of cosmetic compositions intended for the photoprotection (UV-A and/or I/V-B) of human skin are known to this art.
These photoprotective/sunscreen compositions are typically oil-in-water emulsions (namely, a cosmetically acceptable vehicle, carrier or diluent comprising an aqueous continuous dispersing phase and an oily discontinuous dispersed phase) which contains, in various concentrations, one or more standard lipophilic and/or hydrophilic organic sunscreen compounds capable of selectively absorbing harmful or deleterious UV radiation. These sunscreen compounds (and the amounts thereof) are selected as a function of the desired sun protection factor (the sun protection factor (SPF) being expressed mathematically by the ratio of the irradiation time required to attain the erythema-forming threshold with the UV screening agent to the time required to attain the erythema-forming threshold in the absence of UV screening agent).
Thus, EP-A-0,457,687 describes a particularly advantageous photoprotective/sunscreen combination comprising immixture of a hydrophilic UV-A screening compound, namely, benzene-1,4-di(3-methylidene-10-camphorsulfonic)acid, and a lipophilic UV-B screening compound, namely, 2,4,6-tris[p-((2'-ethylhexyl)oxycarbonyl)anilinol]1,3,5-triazine. This admixture presents the principal advantages of providing nontoxic sunscreen compositions which, on the one hand, via a synergistic effect between the two screening compounds, exhibit high protection factors over a wide UV wavelength range (280-400 nm), which, on the other, are thermally and photochemically stable, and also which have good cosmetic properties. However, the sun protection factors on skin imparted by the subject compositions may, and particularly in respect of the so-called sensitive skin types and/or for skin continually exposed to the sun, still appear to be insufficient.
Therefore, need continues to exist in this art for even more efficacious photoprotective/cosmetic compositions.